Radiation-polymerizable cellulose esters

Abstract

The present invention relates to a grafted cellulose ester prepared by reacting a cellulose ester containing residual hydroxyl groups with an acrylic based compound and m-isopropenyl-α,α'-dimethylbenzyl isocyanate. The grafted cellulose ester is a urethane-containing product having pendant (meth)acrylate and α-methylstyrene moieties. The grafted cellulose ester is readily self-polymerizable in the presence of a photoinitiator upon exposure to ultraviolet radiation. It does not require the presence of vinyl monomers to become crosslinked. The grafted cellulose ester is useful as a protective/decorative coating for wood, metal, plastics, and other substrates.

I claim: 
     
       1. An ethylenically unsaturated self-crosslinkable grafted cellulose ester of the formula ##STR5## wherein: R 1  is a (meth)acrylate moiety of the formula ##STR6## R 2  is α-methylstyrene moiety of the formula ##STR7## R 3  is, independently, H, ##STR8## x is about 0.1 to 2.5, y is about 0.1 to 2.0,   z is about 0.1 to 2.0, and   n is 30-250,    provided that (x+y+z) is in the range of 0.3 to 3.0.   
     
     
       2. The cellulose ester of claim 1 wherein x is about 0.1 to 0.25, y is about 0.1 to 0.5, and z is about 0.1 to 0.9. 
     
     
       3. A coating composition comprising (a) An ethylenically unsaturated self-crosslinkable grafted cellulose ester of the formula ##STR9##  wherein: R 1  is a (meth)acrylate moiety of the formula ##STR10## R 2  is α-methylstyrene moiety of the formula ##STR11## R 3  is, independently, H, ##STR12## x is about 0.1 to 2.5, y is about 0.1 to 2.0, z is about 0.1 to 2.0, and   n is 30-250,    provided that (x+y+z) is in the range of 0.3 to 3.0, and     (b) a solvent in an amount sufficient to solubilize (a)   
     
     
       4. The coating composition of claim 3 wherein said suitable solvent is acetone, 2-butanone, 2-pentanone, ethyl acetate, propyl acetate, butyl acetate, chlorobenzene, or toluene. 
     
     
       5. The coating composition of claim 3 further comprising a urethane bond-forming catalyst or a polymerization inhibitor. 
     
     
       6. The coating composition of claim 3 wherein said solvent is present in an amount of about 60 to about 90 weight % of the total composition. 
     
     
       7. The coating composition of claim 3 further comprising acrylic acid, methacrylic acid, acrylic anhydride or methacrylic anhydride. 
     
     
       8. The coating composition of claim 3 further comprising from about 0.1 to about 5 weight % of a leveling agent, based on the weight of the total composition. 
     
     
       9. The coating composition of claim 3 further comprising from about 2 to about 7 weight % of a photoinitiator, based on the weight of the total composition. 
     
     
       10. The composition of claim 9 wherein said photoinitiator is present in an amount of about 3 to about 5 weight % of the total composition. 
     
     
       11. An article comprising (a) a substrate, and   (b) a coating thereon comprising a polymerized ethylenically unsaturated self-crosslinkable grafted cellulose ester of the formula ##STR13##  wherein: R 1  is a (meth)acrylate moiety of the formula ##STR14## R 2  is α-methylstyrene moiety of the formula ##STR15## R 3  is, independently, H, ##STR16## x is about 0.1 to 2.5, y is about 0.1 to 2.0, z is about 0.1 to 2.0, and   n is 30-250,   provided that (x+y+z) is in the range of 0.3 to 3.0.     
     
     
       12. The article of claim 11 wherein said coating has a solvent resistance of at least 200 rubs using ASTM Procedure D-3732, and a pencil hardness of greater than or equal to F using ASTM Procedure D3363. 
     
     
       13. The article of claim 12 wherein said coating has a pencil hardness of greater than or equal to H using ASTM Procedure D3363. 
     
     
       14. A process for preparing an ethylenically unsaturated self-crosslinkable grafted cellulose ester of the formula ##STR17## wherein: R 1  is a (meth)acrylate moiety of the formula ##STR18## R 2  is α-methylstyrene moiety of the formula ##STR19## R 3  is, independently, H, ##STR20## x is about 0.1 to 2.5, y ix about 0.1 to 2.0, z is about 0.1 to 2.0, and   n is 30-250,   provided that (x+y+z) is in the range of 0.3 to 3.0, comprising: reacting     (a) (meth)acrylic anhydride, or a mixture of (meth)acryloyl halide and a hydrogen acceptor, with   (b) an intermediate reaction product of (i) a cellulose ester of cellulose and at least one saturated monocarboxylic acid having 2 to 4 carbon atoms, wherein said cellulose ester has a degree of substitution per anhydroglucose unit of residual hydroxyl groups of about 0.1 to 2.0, and   (ii) meta-isopropenyl-2,2'-dimethylbenzyl isocyanate or para-isopropenyl-2,2'-dimethylbenzyl isocyanate, in the presence of a solvent and under conditions such that the desired product is formed.       
     
     
       15. The process of claim 14 carried out at a temperature between about 40° to 60° C. 
     
     
       16. The process of claim 14 carried out in the presence of a polymerization inhibitor in an amount of about 0.01% to about 1.0 weight % based on the weight of grafted cellulose ester. 
     
     
       17. The process of claim 14 wherein said cellulose ester has a degree of substitution per anhydroglucose unit of residual hydroxyl groups of about 0.3 to 0.9. 
     
     
       18. The process of claim 14 wherein said suitable solvent is acetone, 2-butanone, ethyl acetate, 2-pentanone, butyl acetate, propyl acetate, chlorobenzene, or toluene. 
     
     
       19. A process for preparing an ethylenically unsaturated self-crosslinkable grafted cellulose ester of the formula ##STR21## wherein: R.sup. 1 is a (meth)acrylate moiety of the formula ##STR22## R 2  is α-methylstyrene moiety of the formula ##STR23## R.sup. 3 is, independently, H, ##STR24## x is about 0.1 to 2.5, y is about 0.1 to 2.0, z is about 0.1 to 2.0, and   n is 30-250,   provided that (x+y+z) is in the range of 0.3 to 3.0,   comprising: reacting   (a) meta-isopropenyl-2,2'-dimethylbenzyl   isocyanate or para-isopropenyl-2,2'-dimethylbenzyl isocyanate, with   (b) an intermediate reaction product of (i) a cellulose ester of cellulose and at least one saturated monocarboxylic acid having 2 to 4 carbon atoms, wherein said cellulose ester has a degree of substitution per anhydroglucose unit of residual hydroxyl groups of about 0.1 to 2.0, and   (ii) (meth) acrylic anhydride, or (meth)acryloyl halide and a hydrogen acceptor,      in the presence of a solvent and a catalytic amount of a urethane bond-forming catalyst and under conditions such that the desired product is formed.   
     
     
       20. The process of claim 19 carried out and at a temperature between about 60° to 160° C. 
     
     
       21. The process of claim 19 carried out in the presence of a polymerization inhibitor. 
     
     
       22. The process of claim 19 wherein said cellulose ester has a degree of substitution per anhydroglucose unit of residual hydroxyl groups of about 0.3 to 0.9. 
     
     
       23. The process of claim 19 wherein said suitable solvent is acetone, 2-butanone, ethyl acetate, 2-pentanone, butyl acetate, propyl acetate, chlorobenzene or toluene; and said catalytic amount of urethane bond-forming catalyst is about 0.1 to about 5.0 weight % based on the weight of ungrafted cellulose ester starting material. 
     
     
       24. The process for facilitating isolating an ethylenically unsaturated self-crosslinkable grafted cellulose ester of the formula ##STR25## wherein: R 1  is a (meth)acrylate moiety of the formula ##STR26## R 2  is α-methylstyrene moiety of the formula ##STR27## R 3  is, independently, H, ##STR28## x is about 0.1 to 2.5, y is about 0.1 to 2.0,   z is about 0.1 to 2.0, and   n is 30-250,   provided that (x+y+z) is in the range of 0.3 to 3.0   and wherein said cellulose ester is in unprecipitated form and is in a mixture with reaction by-products and a solvent,   comprising: contacting said mixture with an amount of nonsolvent sufficient to precipitate the desired product.   
     
     
       25. The process of claim 24, including the additional step of separating the precipitated product from unprecipitated by-products. 
     
     
       26. The process of claim 25 wherein said nonsolvent is selected from the group consisting of water, methanol, ethanol, isopropanol, hexane, heptane and mixtures thereof.